1. Field of the Disclosure
This disclosure relates generally to semiconductors, and more specifically, to data processors that implement a debug mode of operation.
2. Description of the Related Art
An IEEE standard known as IEEE ISTO5001, or the Nexus debug standard, is an established real-time debug standard that supports real-time debug message generation. The Nexus debug standard specifies a mechanism for identifying to an external trace reconstruction tool a predetermined operating condition within the system. Debugging processes are also used in the development of code for a data processing system. Providing debug information in real-time, without intrusion on the normal operation of the data processing system, is highly desirable to remain transparent to operation of the system.
Debug messages include trace messages that are generated by the data processing system. Trace messages can contain address and data information for either program events (program trace messaging) that relates to the execution sequence of instructions, or to data events (data read messaging, data write messaging). The address information is typically virtual address information that must be translated to identify a physical memory location known as a physical address. Correlation of virtual address information associated with debug messages to physical address information allows a debug tool a straight forward mechanism to trace programs via a listing of instructions obtained at static compile and link time that uses virtual address. However, an issue arises when such a listing is unavailable for pre-compiled software modules that are executed at runtime, such as OS cells, library functions, etc. In this case, no program listing is available making it difficult to properly trace and interpret these sections of code when executed. In such situations, the inability to deterministically translate virtual addresses to physical addresses can preclude debug message generation from being performed real-time.